Process for converting into soluble salts lead and other metals contained in lead bearing ores



Patented Apr. 25, 1933 PATENTTOF'FICE? UNITED STATES PAUL GAMICHON, OF PARIS, FRANCE PROCESS FOR CONVERTING INTO SOLUBLE SALTS LEAD ANI JOTHER METALS CONTAINED p IN LEAD BEARING ORES No Drawing. Application filed June 12, 1931, Serial No. 3,819, and in France Jiine 17, 1930.

The various known processes for roasting lead'bearing' sulphide ores with a view to their subsequent treatment by dissolution and wet meansmay be restricted to two:

5 (1) Sulphating roasting. In this case, the.

conversion of the sulphide ore is somewhat slow and difficult to carry out It is, furtherly sulphates and chlorides which have been more, always veryincomplete. y

(2) Chlorinating roasting. In this case, to be complete, the reaction requires a considerable excess of alkaline .or earth-alkaline chloride, the cost of which renders its use prohibitive. It requires a somewhathigh temperature (dark red at least) whereby considerable volatilization of theheavy metal chlorides is caused and especially those of lead. Furthermore, neither of these roasting processes can be used successfully to bring to the condition of soluble salts the whole of the metals contained in the ores. If roasting is continued too long or if too high a tempera ture is applied, oxides are formed, and sometimes even the metal itselfis reached and in all cases heavy losses are incurred due to the volatilization ofthe sulphate or chloride' The process pursuant to this invention consists essentially in combining a chlorinating and sulphating roasting with a subsequent 39 treatment of the roasted material by means of a strong acid and thereafter by means of a brine.

The first step consists in roasting the ore in the presence of both a small quantity of sulphate of lime and of a quantity of alkaline chloride or of earth-alkaline chloride which is very much less than the theoretical amount needed to chlorinate the whole of the lead. The ore is thereby very quickly rid of sulphur while furnishing a mixture of lead chloride and sulphate.

It would appear that, in point of fact, the alkaline or earth-alkaline chloride used acts only as a catalytic agentin the desulphuriz- 5 ing of the lead.

The process may be carried out in an ordinary roasting oven (Wedge or any other) with an air inlet and it requires a moderate temperature only.

The reaction so obtainedis much faster acid and more complete than is the case in roastng which is solely sulphating, notwithstand- 111g the small proportion of added chloride. By this means, furthermore, all formation of oxide (PhD) is practically avoided, which is impossible in the case of sulphating roasting.

The roasted material, containing especialformed, is then treated by means of a small, quantity of strong acid, corresponding only to the quantity ofsulphide which has not been converted. by roasting. t

Should the acid used be sulphuric acid, the traces of galena or of sulphides which have not been converted, together with the traces of oxidesyare converted into sulphates. V The sulphates of soluble metals (Zn, Cu, etc.) are easily separated by washing and their solutions may be treated subsequently byIone of the usual methods. n

place of sulphuric'acid, hydrochloric and other strong acids having the same properties may be used, with corresponding differences in results with respect to the salts obtained. u o

If the remainder of the roasted ore be thereafter washed hot with brine, the whole of the'lead and silver is recoveredas soluble chlorides, which is impossible with any of the known roasting processes.

The chloride of lead thus obtained may be crystallized or be used forthe preparation of metallic lead or compounds thereof by any known method. I 7 u The process isexemplified by'the following illustration which does not restrict the scope of the invention: a

1000 kg of ore is crushed, which contains as sulphides 300kg lead and 150-kg zinc, as well as 400 grams silver and 1500 grams copper, so that the whole is adapted to pass through a sieve of approximately 20 mesh.

The ore thus crushed is thereupon mixed with kg at least of chloride of sodium and 20 kg OaSO and the whole mass is roasted in an oxidizing atmosphere, the temperature being gradually raised to 460-490 0.

As soon as thistemperature is reached, reaction takes place almost immediately.

The roasted ore is thereupon washed with 1 500 litres of water containing litres SOH at 53-55 B. This washing completes the conversion of the insoluble salts into soluble salts and the whole of the zinc, copper and other soluble metals may be eliminated by lixiviation and filtration.

The remaining roasted ore which contains lead, is then lixiviated with 4 cubic metres of a brine containing at least 250 grammes of NaClper litre and a total quantity of 6 litres of commercial HCl (22 B.). The solution The silver, for'example, may be precipitate ed in mother-lyes containing spongious lead obtained in any known manner. er-lyescontaining lead may be used afresh, to dissolve the lead contained in the roasted ore'of another cycle of operations.

I claim:

1. Process for converting intosoluble salts metals contained in lead bearing sulphide ores, which consists in roasting said ores at a moderate temperature in the presence of a small quantity of sulphate of lime and of alkaline or earth-alkaline chlorid, then in treating the roasted material successively with a strong acid having the property'of converting into soluble salts the sulphides or traces of oxides left unconverted after -ro'asting, lixiviating the mass to separate the salts ofsoluble metals, such as those of zinc or copper, and treating with a brine to bring into solution the lead, the silver and the metals associated therewith.

2. Process for converting into soluble salts metals contained in lead bearing sulphide ores, whichconsists in'roasting said ores at a moderate temperature in the presence of a small quantity of sulphate oflime and of alkaline or earth-alkaline chlorid, then in treating the roasted material withsulphuric acid to convert into sulphates thesulfides or traces of oxides left unconverted after roasting, and in lixiviating the mass to separate the salts of soluble metals, such as those-of zinc or copper, and in treating with a brine to bring into solution the lead, the silver and the metals associated therewith.

3. Process for converting into soluble salts metals containedjin lead bearing sulphide The mothchloric acid to convert into chlorides the sulfides or traces of oxides left unconverted after roasting, and in lixiviating the mass to separate the salts of soluble metals, such as those of zinc or copper, and in treating with a brineto bring into solution the lead, the silver and the metals associated therewith.

, 4. Process for converting into soluble salts metals contained in lead bearing sulphide ores, which consists in roasting said ores at a moderate temperature in the presence of a 1 small quantity of sulphate of lime and of alkaline or earth-alkaline chlorid used in much smaller quantity than the theoretic amount required to chlorinate the, whole of the lead of the ore, then in treating the roasted material successively by a strong acid having the property of 'convertinginto soluble salts the sulphides or traces of oxides left unconverted after roasting, and then with a brine.

5. Process for converting'into soluble salts metals contained in lead bearing sulphide ores, which consists in roasting said ores at a moderate temperature n the presence of a small quantity of sulphate of lime and of alkaline ore'arth 'alkaline chlorid, in treating the roasted material by sulphuric acid so as to convert intosulphates the sulfides or traces of oxides left unconverted after roasting, and

in lixiviating the mass to separate the salts of soluble metals, such as those 'ofzinc or copper, and in treating with a brine to bring into solution the lead, the silver and the metals as sociated therewith, and finally in filtering the hot liquor obtained after precipitation of metals other than leadand silver and in cool ing said liquor for the crystallization of the chloride of lead.

In testimonywhereof I have signed this specification. PAUL GAMIOHON.

ores, which consists in roasting said ores at a moderate temperature in theipresence of a small quantity of sulphate of lime and of alkaline or earth-alkaline chlorid, then in treating the roasted material with hydro 

